The purpose of this research proposal is to test a model of collective decision-making in a situation called the N-person Prisoner's Dilemma Game (the NPD). In this situation, each person in the group is faced with a conflict between maximizing personal gain (individual interests) and maximizing mutual gain (social welfare). Yet, if everyone attempted to maximize their selfish interests, everyone would be worse off than if everyone cooperated and attempted to maximize the social welfare. The NPD, therefore, is a prototype of many critical problems facing society. From a long range perspective, empirical studies of the NPD may provide valuable insights into the nature of cooperative behavior in such real-life situations. To test the predictions of the model, two types of variables will be manipulated in a laboratory situation: the size of the group, partitioning of the group into smaller subsets, and the reward structure (payoff values) of the situation. In later years of the project, attempts will be made to determine the most effective means of inducing higher levels of cooperation in such dilemma-type situations.